A hybrid 180.degree. microwave balun device is provided to convert an unbalanced RF signal at the common port into two radio frequency signals with equal amplitude and 180.degree. phase difference at two differential ports. The hybrid device includes a coplanar waveguide connecting to the common port. A power divider separates the coplanar waveguide into two symmetrical slotline waveguides to carry balanced signals. Two broadband multioctave slotline to microstrip transitions constructed in a way that the microstrip lines carry 180.degree. phase separated signals to the differential output ports.